<?php
$data = array(
    array(
        "article_id" => "O3fIuC3Ei4Leso0WUTK4Pv384tfvAFgAJLZAPodOwz4",
        "content" => array(
            "news_item" => array(
                'is_deleted' => 'true'
            ),
            "create_time" => 1641778653,
            "update_time" => 1641778660
        ),
        "update_time" => 1641778660
    ),
    array(
        "article_id" => "O3fIuC3Ei4Leso0WUTK4Pv384tfvAFgAJLZAPodOwz5",
        "content" => array(
            "news_item" => array(
                'is_deleted' => 'false'
            ),
            "create_time" => 1641778653,
            "update_time" => 1641778660
        ),
        "update_time" => 1641778660
    ),
    array(
        "article_id" => "O3fIuC3Ei4Leso0WUTK4Pv384tfvAFgAJLZAPodOwz5",
        "content" => array(
            "news_item" => array(
                'is_deleted' => 'false'
            ),
            "create_time" => 1641778653,
            "update_time" => 1641778660
        ),
        "update_time" => 1641778660
    )
);
foreach ($data as $key => $value) {
    if ($value['content']['news_item']['is_deleted'] == 'true') {
        unset($data[$key]);
    }
}
echo "<pre>";
var_dump($data);
echo "</pre>";
die();